Breast-biopsy options have changed considerably over time. In part, biopsy methods have changed in order to keep up with new developments in the detection and diagnosis of breast cancer. Advances in imaging have been prominent among these developments, and the broadest range of biopsy techniques yet seen in medicine is now in clinical use. While open surgical biopsies are still commonly performed, image-guided needle biopsies are preferable under many circumstances.
At one time, breast lumps found during physical examinations or noted during a patient’s self-examination were usually removed completely during excisional biopsy. This procedure was performed in an operating room while the patient was under general anesthesia, and palpation was used to guide the surgeon to the mass to be excised. If, during surgery, it was possible to remove only a portion of the area involved, the procedure was referred to as incisional biopsy.
Open biopsy can be associated with significant cosmetic defects. While these can be minimized by highly skilled, well trained surgeons, a poor cosmetic result may still be inevitable if the mass to be excised is large. The use of image-guided biopsy is the subject of controversy where large lesions are concerned, but it may still be preferred for palpable masses because its use can ensure that the mass has been sampled properly, with the resulting histological information being helpful in later patient care. For example, most surgeons want to be sure a cancer is invasive before doing a biopsy of the axillary nodes.
If the patient who has a palpable benign mass on imaging has decided before biopsy that she wants to have the mass removed, then surgical excision remains the procedure of choice and a core biopsy is not indicated. Any other biopsy method would simply add an unnecessary expense to the patient’s management. Pressures favoring cost-effectiveness in medicine continue to mount, so it is important to avoid subjecting the patient to two procedures where one will do.
With the advent of mammography screening, the surgeon’s task in performing an open breast biopsy became much more difficult. Palpable masses had once been the only lesions subjected to excisional biopsy, but far smaller abnormalities could be detected mammographically. For this reason, the surgeon could no longer count on feeling the suspicious area; this made it hard to be certain that the correct area had been sampled.
In response to this problem, techniques were developed to help the surgeon localize the suspicious lesion more reliably. An intricate system of mapping was first used to show the relationship between the abnormal area and the surface landmarks of the breast. A second technique, specimen radiography, involved radiographic examination of the biopsy specimen to determine whether it matched the abnormal mammography findings; this improved the odds that the intended target had actually been removed for examination.
Although these two techniques were viewed as helpful, it was still necessary to excise a large amount of tissue in order to be certain that the lesion had been removed. At the same time, the use of mammography spread. With smaller abnormalities being detected, the number of excisional biopsies naturally increased. In order to avoid the removal of excessive amounts of breast tissue, radiologists focused on developing better ways of pinpointing lesions for surgical removal.
Toward this end, guided by mammograms, radiologists began placing radiopaque markers directly over suspicious areas. These markers on the breast’s surface were then used during surgery to ensure better localization of lesions. Soon after, the injection of dye into the lesion and the needle track leading to it were employed to enhance surgical guidance. To increase precision still further, dye-injection needles were left in place until surgery. This was followed by the development of hookwire systems that could hold needles or wire in place very near the area of questionable findings. This permitted the amount of excised tissue to be decreased while the accuracy of sampling was retained.
All of these image-guided methods still required open biopsy, which is the gold standard against which later developments would be measured. When a suspicious mass is removed in its entirety (as verified using specimen radiography), sampling error is almost nonexistent. With the involvement of two experts-the experienced radiologist who localizes a lesion and the experienced surgeon who removes it-the failure rate for the excision of nonpalpable abnormalities is less than 2% (although the medical literature varies on this point).
The first alternative to open biopsy, called fine-needle aspiration cytology (FNAC) or fine-needle aspiration biopsy (FNAB), was developed in Europe for use with palpable masses. Its logical application to nonpalpable lesions under stereotactic guidance was introduced in Sweden in 1979 by Nordenstr?m and Zajieck. During the decade that followed, the technique was widely used in Europe to evaluate most abnormal mammographic findings, and it replaced open biopsy to a large degree. Ultrasound was used to guide FNAC during the latter half of the 1980s. The fine-needle aspiration method, however, met with only limited success in the United States. Several factors contributed to this delay in adoption. Too few skilled cytologists were available to evaluate fine-needle aspiration specimens. In addition, needle placement was not always precise. There was also some hesitation to use the fine-needle because of possible exposure to medical liability. Furthermore, because of reports of relatively large numbers of false negatives, specimens obtained through FNAC did not permit interpreters to determine whether the abnormalities noted represented carcinoma in situ, invasive carcinoma, or atypical hyperplasia. The diagnostic accuracy reported for the procedure in the literature varied widely, as well.
In an attempt to establish a uniform approach to FNAB of the breast, the National Cancer Institute of the National Institutes of Health convened a consensus conference in September 1996. Guidelines for performing FNAB and interpreting its results were established by the conference. The group recommended the use of two to four passes of up to 15 up-and-down motions each, employing a 22-gauge to 25-gauge needle.
Accuracy, in needle biopsy, clearly depends on imaging for needle placement. Having mammographic guidance available from two different angles greatly improves the accuracy of needle placement by identifying the depth of the lesion within the breast. This stereotactic biopsy method is supported by two primary equipment configurations, upright and prone. In prone stereotactic biopsy, the patient lies, face downward, on a table dedicated to this purpose. The breast, accessible through an opening in the table, is compressed and held while the biopsy is performed by the radiologist and technologist, who are typically seated beneath the elevated table. Use of the prone table prevents vasovagal reactions such as loss of consciousness and can permit examinations to be completed more rapidly. This type of system is now more widely used but its more expensive than an upright unit. The prone table also requires more space.
Upright stereotactic biopsy equipment that fits on a mammography unit is typically less expensive, and it often allows use of the space for mammography examinations between biopsy patients. The radiologist and technologist have less room to work, however, and vasovagal reactions are possible. Some women may also find it difficult to remain still during the procedure if they are in a seated position.
Core-needle biopsy (CNB) using an automated large-core (ALC) gun was introduced in Sweden by Lindgren in 1982. It was adapted to stereotactic breast biopsies in 1990, by Parker. Later, ultrasound guidance for breast core-needle biopsy was introduced. The two guidance methods led to a revolution in US breast-biopsy methods, with CNB reaching wide dissemination and rapid adoption.
Breast CNB uses 18-gauge, 16-gauge, or the preferred 14-gauge needles that have a throw of 1 cm to 2.5 cm into the breast in order to obtain specimens. Typically, five or fewer specimens are obtained for masses and 10 or more are needed to evaluate calcifications. CNB provides larger samples than FNAB, and permit pathologists to determine whether a carcinoma is in situ or invasive. A few CNB histological diagnoses, however, require that excisional biopsy be performed
A disposable probe and a reusable probe driver are combined to form the vacuum-assisted device (VAD) used to obtain specimens of breast tissue. A cutting unit within the probe captures tissue that is then removed from the breast using vacuum aspiration. The probe can be guided stereotactically (as originally designed) or using ultrasound. Once the target specimen has been retrieved, a microclip can be inserted to mark the biopsy site.
Vacuum-assisted devices use 14-gauge to 11-gauge needles; the larger needles produce a 70% increase in specimen diameter that is especially helpful in the assessment of calcifications. Specimen retrieval is faster, and samples are more contiguous. The probes can be expensive, however, and there may be additional costs involved if it is necessary to upgrade an older stereotactic system to handle vacuum-assisted biopsies.
MICROCLIP PLACEMENT and DOCUMENTATION
At the end of a stereotactic vacuum-assisted biopsy, a 2-mm stainless steel clip can be placed in the suspicious area directly through the 11-gauge probe. A smaller clip or coil can be introduced through the 14-gauge needle. If the lesion has been entirely removed during the biopsy, the clip or coil can then serve to identify the biopsy site, as well as to identify the tumor bed if nonsurgical cancer therapy later proves necessary.
Biopsy documentation through imaging is important not only for medicolegal reasons, but to ensure that the pathology and imaging results refer to the same lesion. During the biopsy, imaging documentation is used to verify that the specimens came from the target area.
In our practice, for stereotactic biopsy, documentation calls for targeting images at 0? and at ?15? (stereo pairs), along with stereo images before and after firing. Another image is obtained to show immediate changes following the biopsy. Specimen radiography then confirms that the specimen contains calcifications, and postbiopsy mammograms show the location of the microclip, if one was inserted.
For documentation of ultrasound-guided biopsy, prefire images showing the needle proximal to the lesion should be followed by postfire images that show the needle traversing the lesion area.
Whether a radiologist uses ultrasound or stereotactic mammography to guide needle biopsy is often a matter of preference. Ultrasound may be preferred for preoperative needle localization or for needle biopsy of palpable masses. It is more rapid, it permits real-time imaging, and it is likely to be more comfortable for the patient. For nonpalpable lesions visible only mammographically, stereotactic guidance is necessary.
Needle biopsy techniques obviously procure specimens at a lower cost and are less invasive than open biopsy methods. The biopsy itself may be easier and less expensive, but patients who would not have been sent for open biopsies should not be sent for needle biopsies, either. The recommendation for biopsy threshold should not be lowered simply because we have new biopsy devices, without evidence that patient care and outcomes would be improved. No savings in cost or decrease in patient worry can be produced if biopsy is simply recommended more often. Better care at a lower cost, however, will be obtained when needle biopsy replaces open biopsy for properly selected patients.
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Lawrence W. Bassett, MD, is Iris Cantor Professor of Breast Imaging, UCLA School of Medicine, Los Angeles. This article is based on his presentation at the Fifth Postgraduate Course of the Society of Breast Imaging on May 16, 2001, in San Diego.